CSSJanus.php

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<?php
class CSSJanus {
    // Patterns defined as null are built dynamically by buildPatterns()
    private static $patterns = array(
        'tmpToken' => '`TMP`',
        'nonAscii' => '[\200-\377]',
        'unicode' => '(?:(?:\\[0-9a-f]{1,6})(?:\r\n|\s)?)',
        'num' => '(?:[0-9]*\.[0-9]+|[0-9]+)',
        'unit' => '(?:em|ex|px|cm|mm|in|pt|pc|deg|rad|grad|ms|s|hz|khz|%)',
        'body_selector' => 'body\s*{\s*',
        'direction' => 'direction\s*:\s*',
        'escape' => null,
        'nmstart' => null,
        'nmchar' => null,
        'ident' => null,
        'quantity' => null,
        'possibly_negative_quantity' => null,
        'color' => null,
        'url_special_chars' => '[!#$%&*-~]',
        'valid_after_uri_chars' => '[\'\"]?\s*',
        'url_chars' => null,
        'lookahead_not_open_brace' => null,
        'lookahead_not_closing_paren' => null,
        'lookahead_for_closing_paren' => null,
        'lookahead_not_letter' => '(?![a-zA-Z])',
        'lookbehind_not_letter' => '(?<![a-zA-Z])',
        'chars_within_selector' => '[^\}]*?',
        'noflip_annotation' => '\/\*\!?\s*@noflip\s*\*\/',
        'noflip_single' => null,
        'noflip_class' => null,
        'comment' => '/\/\*[^*]*\*+([^\/*][^*]*\*+)*\//',
        'direction_ltr' => null,
        'direction_rtl' => null,
        'left' => null,
        'right' => null,
        'left_in_url' => null,
        'right_in_url' => null,
        'ltr_in_url' => null,
        'rtl_in_url' => null,
        'cursor_east' => null,
        'cursor_west' => null,
        'four_notation_quantity' => null,
        'four_notation_color' => null,
        'border_radius' => null,
        'box_shadow' => null,
        'text_shadow1' => null,
        'text_shadow2' => null,
        'bg_horizontal_percentage' => null,
        'bg_horizontal_percentage_x' => null,
    );

    private static function buildPatterns() {
        if (!is_null(self::$patterns['escape'])) {
            // Patterns have already been built
            return;
        }

        // @codingStandardsIgnoreStart Generic.Files.LineLength.TooLong
        $patterns =& self::$patterns;
        $patterns['escape'] = "(?:{$patterns['unicode']}|\\[^\r\n\f0-9a-f])";
        $patterns['nmstart'] = "(?:[_a-z]|{$patterns['nonAscii']}|{$patterns['escape']})";
        $patterns['nmchar'] = "(?:[_a-z0-9-]|{$patterns['nonAscii']}|{$patterns['escape']})";
        $patterns['ident'] = "-?{$patterns['nmstart']}{$patterns['nmchar']}*";
        $patterns['quantity'] = "{$patterns['num']}(?:\s*{$patterns['unit']}|{$patterns['ident']})?";
        $patterns['possibly_negative_quantity'] = "((?:-?{$patterns['quantity']})|(?:inherit|auto))";
        $patterns['color'] = "(#?{$patterns['nmchar']}+|(?:rgba?|hsla?)\([ \d.,%-]+\))";
        $patterns['url_chars'] = "(?:{$patterns['url_special_chars']}|{$patterns['nonAscii']}|{$patterns['escape']})*";
        $patterns['lookahead_not_open_brace'] = "(?!({$patterns['nmchar']}|\r?\n|\s|#|\:|\.|\,|\+|>|\(|\)|\[|\]|=|\*=|~=|\^=|'[^']*'])*?{)";
        $patterns['lookahead_not_closing_paren'] = "(?!{$patterns['url_chars']}?{$patterns['valid_after_uri_chars']}\))";
        $patterns['lookahead_for_closing_paren'] = "(?={$patterns['url_chars']}?{$patterns['valid_after_uri_chars']}\))";
        $patterns['noflip_single'] = "/({$patterns['noflip_annotation']}{$patterns['lookahead_not_open_brace']}[^;}]+;?)/i";
        $patterns['noflip_class'] = "/({$patterns['noflip_annotation']}{$patterns['chars_within_selector']}})/i";
        $patterns['direction_ltr'] = "/({$patterns['direction']})ltr/i";
        $patterns['direction_rtl'] = "/({$patterns['direction']})rtl/i";
        $patterns['left'] = "/{$patterns['lookbehind_not_letter']}(left){$patterns['lookahead_not_letter']}{$patterns['lookahead_not_closing_paren']}{$patterns['lookahead_not_open_brace']}/i";
        $patterns['right'] = "/{$patterns['lookbehind_not_letter']}(right){$patterns['lookahead_not_letter']}{$patterns['lookahead_not_closing_paren']}{$patterns['lookahead_not_open_brace']}/i";
        $patterns['left_in_url'] = "/{$patterns['lookbehind_not_letter']}(left){$patterns['lookahead_for_closing_paren']}/i";
        $patterns['right_in_url'] = "/{$patterns['lookbehind_not_letter']}(right){$patterns['lookahead_for_closing_paren']}/i";
        $patterns['ltr_in_url'] = "/{$patterns['lookbehind_not_letter']}(ltr){$patterns['lookahead_for_closing_paren']}/i";
        $patterns['rtl_in_url'] = "/{$patterns['lookbehind_not_letter']}(rtl){$patterns['lookahead_for_closing_paren']}/i";
        $patterns['cursor_east'] = "/{$patterns['lookbehind_not_letter']}([ns]?)e-resize/";
        $patterns['cursor_west'] = "/{$patterns['lookbehind_not_letter']}([ns]?)w-resize/";
        $patterns['four_notation_quantity_props'] = "((?:margin|padding|border-width)\s*:\s*)";
        $patterns['four_notation_quantity'] = "/{$patterns['four_notation_quantity_props']}{$patterns['possibly_negative_quantity']}(\s+){$patterns['possibly_negative_quantity']}(\s+){$patterns['possibly_negative_quantity']}(\s+){$patterns['possibly_negative_quantity']}(\s*[;}])/i";
        $patterns['four_notation_color'] = "/((?:-color|border-style)\s*:\s*){$patterns['color']}(\s+){$patterns['color']}(\s+){$patterns['color']}(\s+){$patterns['color']}(\s*[;}])/i";
        $patterns['border_radius'] = "/(border-radius\s*:\s*)([^;}]*)/";
        $patterns['box_shadow'] = "/(box-shadow\s*:\s*(?:inset\s*)?){$patterns['possibly_negative_quantity']}/i";
        $patterns['text_shadow1'] = "/(text-shadow\s*:\s*){$patterns['color']}(\s*){$patterns['possibly_negative_quantity']}/i";
        $patterns['text_shadow2'] = "/(text-shadow\s*:\s*){$patterns['possibly_negative_quantity']}/i";
        $patterns['bg_horizontal_percentage'] = "/(background(?:-position)?\s*:\s*(?:[^:;}\s]+\s+)*?)({$patterns['quantity']})/i";
        $patterns['bg_horizontal_percentage_x'] = "/(background-position-x\s*:\s*)(-?{$patterns['num']}%)/i";
        // @codingStandardsIgnoreEnd

    }

    public static function transform($css, $swapLtrRtlInURL = false, $swapLeftRightInURL = false) {
        // We wrap tokens in ` , not ~ like the original implementation does.
        // This was done because ` is not a legal character in CSS and can only
        // occur in URLs, where we escape it to %60 before inserting our tokens.
        $css = str_replace('`', '%60', $css);

        self::buildPatterns();

        // Tokenize single line rules with /* @noflip */
        $noFlipSingle = new CSSJanusTokenizer(self::$patterns['noflip_single'], '`NOFLIP_SINGLE`');
        $css = $noFlipSingle->tokenize($css);

        // Tokenize class rules with /* @noflip */
        $noFlipClass = new CSSJanusTokenizer(self::$patterns['noflip_class'], '`NOFLIP_CLASS`');
        $css = $noFlipClass->tokenize($css);

        // Tokenize comments
        $comments = new CSSJanusTokenizer(self::$patterns['comment'], '`C`');
        $css = $comments->tokenize($css);

        // LTR->RTL fixes start here
        $css = self::fixDirection($css);
        if ($swapLtrRtlInURL) {
            $css = self::fixLtrRtlInURL($css);
        }

        if ($swapLeftRightInURL) {
            $css = self::fixLeftRightInURL($css);
        }
        $css = self::fixLeftAndRight($css);
        $css = self::fixCursorProperties($css);
        $css = self::fixFourPartNotation($css);
        $css = self::fixBorderRadius($css);
        $css = self::fixBackgroundPosition($css);
        $css = self::fixShadows($css);

        // Detokenize stuff we tokenized before
        $css = $comments->detokenize($css);
        $css = $noFlipClass->detokenize($css);
        $css = $noFlipSingle->detokenize($css);

        return $css;
    }

    private static function fixDirection($css) {
        $css = preg_replace(
            self::$patterns['direction_ltr'],
            '$1' . self::$patterns['tmpToken'],
            $css
        );
        $css = preg_replace(self::$patterns['direction_rtl'], '$1ltr', $css);
        $css = str_replace(self::$patterns['tmpToken'], 'rtl', $css);

        return $css;
    }

    private static function fixLtrRtlInURL($css) {
        $css = preg_replace(self::$patterns['ltr_in_url'], self::$patterns['tmpToken'], $css);
        $css = preg_replace(self::$patterns['rtl_in_url'], 'ltr', $css);
        $css = str_replace(self::$patterns['tmpToken'], 'rtl', $css);

        return $css;
    }

    private static function fixLeftRightInURL($css) {
        $css = preg_replace(self::$patterns['left_in_url'], self::$patterns['tmpToken'], $css);
        $css = preg_replace(self::$patterns['right_in_url'], 'left', $css);
        $css = str_replace(self::$patterns['tmpToken'], 'right', $css);

        return $css;
    }

    private static function fixLeftAndRight($css) {
        $css = preg_replace(self::$patterns['left'], self::$patterns['tmpToken'], $css);
        $css = preg_replace(self::$patterns['right'], 'left', $css);
        $css = str_replace(self::$patterns['tmpToken'], 'right', $css);

        return $css;
    }

    private static function fixCursorProperties($css) {
        $css = preg_replace(
            self::$patterns['cursor_east'],
            '$1' . self::$patterns['tmpToken'],
            $css
        );
        $css = preg_replace(self::$patterns['cursor_west'], '$1e-resize', $css);
        $css = str_replace(self::$patterns['tmpToken'], 'w-resize', $css);

        return $css;
    }

    private static function fixFourPartNotation($css) {
        $css = preg_replace(self::$patterns['four_notation_quantity'], '$1$2$3$8$5$6$7$4$9', $css);
        $css = preg_replace(self::$patterns['four_notation_color'], '$1$2$3$8$5$6$7$4$9', $css);
        return $css;
    }

    private static function fixBorderRadius($css) {
        $css = preg_replace_callback(self::$patterns['border_radius'], function ($matches) {
            $pre = $matches[1];
            $values = $matches[2];
            $numValues = count(preg_split('/\s+/', trim($values)));
            switch ($numValues) {
                case 4:
                    $values = preg_replace('/^(\S+)(\s*)(\S+)(\s*)(\S+)(\s*)(\S+)/', '$3$2$1$4$7$6$5', $values);
                    break;
                case 3:
                case 2:
                    $values = preg_replace('/^(\S+)(\s*)(\S+)/', '$3$2$1', $values);
                    break;
            }
            return $pre . $values;
        }, $css);

        return $css;
    }

    private static function fixShadows($css) {
        // Flips the sign of a CSS value, possibly with a unit.
        // (We can't just negate the value with unary minus due to the units.)
        $flipSign = function ($cssValue) {
            // Don't mangle zeroes
            if (floatval($cssValue) === 0.0) {
                return $cssValue;
            } elseif ($cssValue[0] === '-') {
                return substr($cssValue, 1);
            } else {
                return "-" . $cssValue;
            }
        };

        $css = preg_replace_callback(self::$patterns['box_shadow'], function ($matches) use ($flipSign) {
            return $matches[1] . $flipSign($matches[2]);
        }, $css);

        $css = preg_replace_callback(self::$patterns['text_shadow1'], function ($matches) use ($flipSign) {
            return $matches[1] . $matches[2] . $matches[3] . $flipSign($matches[4]);
        }, $css);

        $css = preg_replace_callback(self::$patterns['text_shadow2'], function ($matches) use ($flipSign) {
            return $matches[1] . $flipSign($matches[2]);
        }, $css);

        return $css;
    }

    private static function fixBackgroundPosition($css) {
        $replaced = preg_replace_callback(
            self::$patterns['bg_horizontal_percentage'],
            array('self', 'calculateNewBackgroundPosition'),
            $css
        );
        if ($replaced !== null) {
            // preg_replace_callback() sometimes returns null
            $css = $replaced;
        }
        $replaced = preg_replace_callback(
            self::$patterns['bg_horizontal_percentage_x'],
            array('self', 'calculateNewBackgroundPosition'),
            $css
        );
        if ($replaced !== null) {
            $css = $replaced;
        }

        return $css;
    }

    private static function calculateNewBackgroundPosition($matches) {
        $value = $matches[2];
        if (substr($value, -1) === '%') {
            $idx = strpos($value, '.');
            if ($idx !== false) {
                $len = strlen($value) - $idx - 2;
                $value = number_format(100 - $value, $len) . '%';
            } else {
                $value = (100 - $value) . '%';
            }
        }
        return $matches[1] . $value;
    }
}

class CSSJanusTokenizer {
    private $regex;
    private $token;
    private $originals;

    public function __construct($regex, $token) {
        $this->regex = $regex;
        $this->token = $token;
        $this->originals = array();
    }

    public function tokenize($str) {
        return preg_replace_callback($this->regex, array($this, 'tokenizeCallback'), $str);
    }

    private function tokenizeCallback($matches) {
        $this->originals[] = $matches[0];
        return $this->token;
    }

    public function detokenize($str) {
        // PHP has no function to replace only the first occurrence or to
        // replace occurrences of the same string with different values,
        // so we use preg_replace_callback() even though we don't really need a regex
        return preg_replace_callback(
            '/' . preg_quote($this->token, '/') . '/',
            array($this, 'detokenizeCallback'),
            $str
        );
    }

    private function detokenizeCallback($matches) {
        $retval = current($this->originals);
        next($this->originals);

        return $retval;
    }
}